How to Talk to a Capsule Manufacturer About Your Format Needs
Most supplement brands come to a capsule manufacturer knowing what’s in the product but not how it should be delivered. That’s the gap that slows projects down. “Format” — the capsule size, the shell material, and the fill type — determines your per-dose cost, how many capsules a customer swallows per serving, how long your product stays stable on a shelf, and which filling equipment can run your batch. Get those three decisions right early and the rest of the project moves quickly. Get them wrong and you can find yourself reformulating after you’ve already printed labels and ordered bottles.
This guide covers what each of those decisions actually involves, with the numbers and tradeoffs you’ll want in hand before your first conversation.
Capsule size: it’s a volume decision, not a milligram decision
This is the single most common point of confusion. Capsule sizes are numbered backwards — the larger the number, the smaller the capsule — and they describe volume, not weight. A size 000 is the largest standard capsule; a size 5 is the smallest.
Here’s the part brands miss: how many milligrams fit in a given size depends entirely on the bulk density of your powder. A dense mineral blend and a fluffy herbal extract can differ by 2x or more in the same shell. The figures below assume a typical powder density of about 0.8 g/mL and should be treated as planning estimates, not guarantees:
| Size | Volume (mL) | Approx. fill at ~0.8 g/mL | Typical use |
|---|---|---|---|
| 000 | ~1.37 | ~800–1,300 mg | High-dose single actives, bulky fibers |
| 00 | ~0.95 | ~600–750 mg | Most popular for high-potency supplements |
| 0 | ~0.68 | ~400–500 mg | Moderate doses; common all-rounder |
| 1 | ~0.50 | ~300–400 mg | Lower doses, easier swallowing |
| 2 | ~0.37 | ~200–300 mg | Smaller doses |
| 3 | ~0.30 | ~150–200 mg | Sensitive markets |
| 4 | ~0.21 | ~100–150 mg | Children’s or pet formulas |
| 5 | ~0.13 | ~60–130 mg | Smallest standard size |
The practical math: to find the size you need, divide your target dose by your powder’s bulk density. If you want 650 mg per capsule and your blend runs 0.70 g/mL, that’s 650 ÷ 700 = 0.93 mL — which lands you in size 00 territory. If the same dose came in a fluffier 0.45 g/mL blend, you’d need ~1.44 mL and would be looking at a 000, or splitting the dose across two capsules.
Sizes 00 and 0 cover the large majority of commercial supplements because they balance capacity against swallowability. If you’re only slightly over capacity, ask about elongated capsules (00E, 0E) before jumping to a larger size — they add a little volume without a big jump in length, and they’re often a cleaner fix than reformulating. And remember the human factor: a 000 capsule is over 26 mm long, which a lot of older customers won’t take comfortably. Sometimes two smaller capsules beat one giant one for repeat purchases.
Shell material: gelatin, HPMC, or pullulan
The shell isn’t just a container. It affects dietary claims, shelf stability, dissolution, and cost. There are three main options.
Gelatin is the traditional, lowest-cost, most widely available shell. It dissolves quickly and predictably, and consumers recognize it. Its drawbacks: it’s animal-derived (so no vegan, and harder for halal/kosher claims), it has a relatively high moisture content, and it’s hygroscopic — it can absorb or release moisture and is sensitive to heat. That makes it a poorer fit for moisture-sensitive ingredients and for shipping or storage in hot, humid conditions.
HPMC (hydroxypropyl methylcellulose, made from plant cellulose) is the workhorse vegetarian option. It’s plant-based, allergen-free, and suitable for vegan, halal, and kosher claims. Its real technical advantage is low moisture content (~3–8%), which protects hygroscopic ingredients and holds up better in heat and humidity. It costs moderately more than gelatin but is widely available. This is usually the right default for a clean-label or moisture-sensitive product.
Pullulan (a polysaccharide from fermented tapioca) is the premium option. It’s also vegan-friendly and offers the strongest oxygen barrier of the three, which makes it the go-to for oxidation-sensitive actives like probiotics and certain oils. The catch is cost — often 2–3x the price of gelatin — and sometimes longer lead times.
A quick way to decide:
- Cost and consumer familiarity are the priority, no vegan requirement → gelatin
- Vegan/clean-label, or your ingredients pull moisture → HPMC
- Premium positioning, or you need to protect against oxidation (probiotics, delicate oils) → pullulan
Fill type: what goes inside changes everything
Two-piece capsules can hold more than dry powder, and each fill type carries different handling requirements and equipment needs.
Powders and granules are the standard and the most flexible. They run on virtually all filling equipment and give you the most freedom on blend composition.
Liquids, oils, and semi-solids are possible but more demanding. They typically require band-sealing or a liquid-fill line so the capsule doesn’t leak, and the shell choice matters: HPMC handles most non-aqueous oils and alcohols well, while water-based liquids need special consideration. If your active is an oil or a paste, flag it at the very first conversation, because it changes the equipment and the shell.
Multi-ingredient blends raise a practical question worth raising upfront: do any of your ingredients react with each other, attract moisture, or need to be kept apart? That can affect whether a single capsule works or whether you need a different approach.
Delivery and release
Standard capsules — gelatin, HPMC, and pullulan — break down quickly in the stomach, which is what most supplements want. If your product needs delayed or targeted release (for example, an ingredient you want to survive stomach acid and release in the intestine), that’s a specialized format involving enteric coatings or acid-resistant shells. It’s a different conversation with different costs and timelines, so name it early if it’s a requirement rather than discovering it late.
What to bring to your first conversation
You don’t need everything finalized, but a few things let a manufacturer give you real answers instead of ballpark guesses:
- A draft formula or ingredient list, ideally with target dose per active. This is what lets anyone estimate capsule size and flag prep steps.
- Your powder’s bulk density, if you have it, or a sample to test. Without it, capsule size is a guess.
- Any dietary or label claims you need — vegan, non-GMO, halal, kosher — since those constrain the shell.
- Target capsule count and serving size, which affect both the size decision and your packaging.
- Your run size and timeline, so production capacity and lead time can be mapped to it.
A note on sequencing
Lock the capsule size before you finalize bottle size, capsule count, and label layout — they all depend on it. A common, avoidable mistake is designing packaging around an assumed capsule size, then discovering the real fill volume needs a larger capsule, a taller bottle, or a split dose. Decide format first, design around it second.
Sorting through sizes, shells, and fill types is genuinely easier with a partner who can test your actual blend rather than work from estimates. Alaska Spring Pharmaceuticals manufactures private-label capsules and other supplement forms at a GMP-compliant facility in Westbury, New York, with typical turnaround of 4–6 weeks. If you’d like help converting a formula into a concrete format spec, reach out to start the conversation.
